Guy's,

98 Ranger, 4x4 4.0L, automatic

Have a problem with my heat & A/C exiting though the defrost vent, regardless of the control head setting, i.e. floor, vents, defrost.

Traced the problem to the PVH selenoid/valve - all part of the same vacuum circuit.

When the vaccum line at the input to the PVH is plugged, the heat & A/C works fine, venting where it should.

Place the PVH back into the vacuum circuit and plug the output end (line going to the hubs), the heat & A/C will only exit to the defrost vent.

Not sure how to test the PVH selenoid/valve??? Want to ensure this is the problem and not the module it connects to.

This is the confusing part. I can hear the hubs lock up when placed in 4WD, with a noticable change in drivability - so the hubs are locking/unlocking.

Help????

Thanks

 

You can probably find something in here: Ranger PVH Diagnostics

Also, maybe adding an inline check valve on the HVAC part of the vacuum circuit will help...

 

Thanks again Rockledge, hadn't been to that site before. The article answers the mail for what I needed.

I think I have ruled out additional vacuum leaks in the lines. Probably the PVH, but need to make sure at $65.00 a pop for a new PVH.

 

Guy's,

98 Ranger, 4x4, 4.0L, automatic

Fixed the problem with both the heat and A/C exiting through the defrost vents, no matter where the control head was set.

Traced the problem to the PVH valve (Pulse Vacuum Hublock).

Also found a cracked vacuum hose on one of the 4x4 hubs - probably contaminated the PVH valve somehow.

This was part of the same vacuum circuit. Using the troubleshooting guide provided by Rockledge was a big help, along with posts by other folks.

Some added details for anyone with a similiar problem, the PVH valve will engage the 4x4 hubs with a vacuum pulse of at least 11in/HG applied for 6-60 seconds. To disengage the hubs, a vacuum pulse of 5.85 to 7.1in/HG applied for 6 to 30 seconds.

For my problem PVH valve, the vacuum pulse to engage the hubs worked fine, about 20in/HG, but to disengage, had the same vacuum, about 20in/HG. The guidance provided by the Ford documentation does not address the issue of to much vacuum, but takes you down the road of testing the electrical aspect of the PVH circuit.

Replacing the PVH valve, about $65.00, fixed the problem. Heat and A/C work fine, the 4x4 hubs lock/unlock fine. As described in other posts, the 4x4 indicator is not a true indicator of your 4x4 status. My hubs were locked with this problem, never unlocking. Noticed an improvement in gas mileage now.

Anyhow, hope this will help someone with the same type of problem.

 

Hey Rock, link doesn't work. Still have the PDF diagnostics file?

 

Try it now. Make sure you copy the file to your hard drive.

 

hehe, Thanks, (good old TSO!) you saved me some time from fishing this out tomorrow at work!

(so is the front driveline supposed to turn at all with disengaged PVH hubs??)

 

Only if the transfer case is engaged in 4WD High or Low.

It's a two stage process. First the TC engages (which connects the front drive shaft and front differential to the transmission), then the PVH solenoid is energized (locking in the hubs at the wheel ends).

 

how do i know if my hubs are engaging or disengaging for sure and w/o jacking up all 4 wheels? -I seem to remember 'feeling' the front driveline in motion in 2WD..! could this be the cause for my crappy mileage? (carrying all the front driveline inertia at all times?)

 

I have 4x4 troubles and this diagnostics manual will come in handy. Thanks, Rockledge. While I'm at it, I might as well ask you what you think it is. My 4x4 intermittently works. Sometimes it engages, sometimes it doesn't. Some times it pops, clunks, and grinds, sometimes it doesn't. If I remember correctly, this all came about after replacing the wheel bearings/hub assemblies - which I've since taken apart God knows how many times trying to see if I did something wrong, check o-rings, lube up, etc.

Last night with the snow we got here in CT, I went to a commuter parking lot, pushed the pedal to the floor to see if the front wheels would also spin... this was my test to check engagement. I finally got them in by playing around with the switch and driving, etc, but I think they eventually disengaged on their own. I also have trouble disengaging. I'll hear a grinding/whining noise which sounds like from the hubs being partially engaged/disengaged. Hubs? TC motor?

Also, what is your impression of permanently engaging the hubs like this...
Permanently Lock Your 1998-2000 Ford Ranger PVH Pulse Vacuum Hubs
??? I was thinking of doing this, effectively making my 99 Ranger more like the newer ones with live axles. Then, that would eliminate the PVH system as the culprit leaving only the TC motor/clutch or much more serious issues. What do you think?

Thanks again for all the help!

-Jay

Also, what else is that manual (looks like the PVH is only the last 30 or so pages)?

 

It does sound like a vacuum leak, probably where you suspect, in the hub assembly. I've read many post describing how difficult it is to get the proper seal once the OEM hubs are repaired/replaced. But you ought to rule out all other possible vacuum leaks as well. If you do a search of this forum using keywords "PVH" and "HVAC", you will find previous threads that cover how to diagnose and repair vacuum leaks. It does not sound like a TC issue, nor a problem with the electronics.

The "Permanent Lock" mod you linked to has proven to work OK, although you might want to consider swapping in some manual locking hubs. Do a search for "AVM", the maker of the manual hubs.

HTH. Good luck.

 

Thanks for the advice. Unfortunately, funds are tight (student loans are kicking my a$$ ) and I don't have the proper tools. I have seen these threads on these issues, but it seems like everyone has a different opinion as to what to do or where exactly the issues are coming in the PVH system (repair ideas/hacks, manual hubs, "permanent lock", transfer case issues, axle issues, all the way to replacing axles)...

And as you say, you've heard of a lot of issues getting the proper seal after replacing the wheel bearings assemblies - which is probably my issue. If this is the situation, there probably isn't much I can do besides rechecking the o-rings and adding grease again, right?

Additionally, the truck is getting pretty old (14 years old since manufacture). It runs pretty well otherwise and looks decent. I've got 170K on it and only paid $5k for it maybe 5 or 6 years ago. I've gotten my money out of it, but don't think it's worth putting much more in, yano? $30-60 for vacuum hand pump + time diagnosing, plus $150-200 for new hubs just doesn't seem worth it to me.

I thank you for all the information. I've seen a lot of your conversations and you are very knowledgeable and helpful. So you're opinion ways heavy in my eyes.